The suit, by three gay couples and a woman who was unable to get recognized on the state death certificate when her longtime, same-sex spouse died, makes Georgia the last Southern state, and one of the last in the nation, to face a challenge to its ban on gay marriage.

"This lawsuit is really about these loving couples trying to protect their families in the same way that different-sex couples can do," said Tara Borelli, senior attorney with Lambda Legal, the national legal group seeking full recognition of the legal rights of lesbians, gay men, bisexuals and transgender people.

Currently, there are 65 pending lawsuits in federal courts of appeal, federal district courts and state courts challenging existing marriage laws in 30 states and Puerto Rico, according to Lambda Legal's analysis.

The U.S. Supreme Court ruled last June, in a decision that struck down the federal Defense of Marriage Act, that the federal government must recognize same-sex marriages performed in states where they're legal. Justice Antonin Scalia said in his dissent that the ruling "arms well every challenger to a state law restricting marriage to its traditional definition." He predicted that suits like the one filed Tuesday in U.S. District Court here were "a second … shoe to be dropped later."

His words seem prophetic: Since that ruling, federal judges in Michigan, Oklahoma, Texas, Utah and Virginia have ruled that state laws banning same-sex marriages were unconstitutional; those decisions are being appealed.

Georgia, where 76% of voters ratified a constitutional amendment to prohibit same-sex marriages in 2004, was late to the table because "there's been an attempt to make strategic decisions about the places where we'd have the best chance of success," Borelli said. "But it became clear as time went on that Georgia should be on that list."

Views on the matter seem to be shifting: A poll in September by The Atlanta Journal-Constitution found that 48% of Georgians favor gay marriage and 43% oppose it.

One of the Georgia couples, Christopher Inniss, 39, and Shelton Stroman, 42, of Snellville, have been together for 13 years, and have a son, Jonathan, 9. They said at a news conference Tuesday that they value their privacy and initially did not want to sue. "At first it was a hard decision, but it became really easy when we thought about our lives," Stroman said, adding that they want Jonathan "to be able to celebrate marriage like his friends do with his parents."

Another plaintiff, Jennifer Sisson, 34, of Decatur, said that her spouse, Pamela Drenner, 49, died in March after a long battle with ovarian cancer. They had married on Valentine's Day 2013 in New York after tests showed Drenner's cancer treatment had apparently succeeded.

Sisson said she was Drenner's caregiver in those final, difficult months. She said she was devastated that she could not be named as spouse on the death certificate. "Having the marriage recognized on the death certificate, you have a chance to re-write your own story in a way," she said. "But 12-14 hours after she died, I was told it was not an option to have the marriage recognized on her death certificate. To have that as kind of the final act … was absolutely, tremendously hard."